WGS 84 Coordinate Validation and Improvement
for the NGA and Air Force GPS Tracking Stations

Abstract: Using 10 days of Global Positioning System (GPS) pseudorange and carrier phase data collected in 1995 from 31 stations and 24 Block II/IA satellites, estimates of GPS clocks, orbits, and tracking station coordinates were generated. The 31 sites consisted of the 12 National Imagery and Mapping Agency (NGA) and Air Force operational stations, an additional NGA site at Holloman Air Force Base, and 18 International GPS Service for Geodynamics (IGS) Rogue receiver sites. Ten of the NGA and Air Force operational sites had their coordinates previously determined using GPS data. The results of this work suggest that the estimated 10 cm, one sigma, per component accuracy indicated for these 10 stations was conservative. The new World Geodetic System 1984 (WGS 84) coordinates generated for the 12 NGA and Air Force operational stations are reported at the 1994.0 and 1997.0 epochs. The estimated accuracy of the new coordinates is better than 5 cm, one sigma, per component.

Orbits estimated using the new WGS 84 coordinates agree better with the IGS final combined orbits, derived in the International Earth Rotation Service Terrestrial Reference Frame 1994, than orbits estimated using the old coordinates. The overall rms orbit-URE of the new orbits is estimated to be 12 cm, an improvement of 2 cm rms over the old orbits. Systematic differences with respect to the IGS orbits have been significantly reduced.

NSWCDD/TR-96/201 November 1996. Approved for public release: distribution unlimited